Make sure initialize() updates the scoped document set

Author: annevk

source

@@ -73816,11 +73816,21 @@ console.assert(el instanceof SpiderMan);    // upgraded!</code></pre>
    <var>root</var>'s <span data-x="shadow-root-custom-element-registry">custom element
    registry</span> to <span>this</span>.</p></li>
 
-   <li><p>For each <span>inclusive descendant</span> <var>inclusiveDescendant</var> of
-   <var>root</var>: if <var>inclusiveDescendant</var> is an <code>Element</code> node whose <span
-   data-x="element-custom-element-registry">custom element registry</span> is null, then set
-   <var>inclusiveDescendant</var>'s <span data-x="element-custom-element-registry">custom element
-   registry</span> to <span>this</span>.</p></li>
+   <li>
+    <p>For each <span>inclusive descendant</span> <var>inclusiveDescendant</var> of <var>root</var>:
+    if <var>inclusiveDescendant</var> is an <code>Element</code> node whose <span
+    data-x="element-custom-element-registry">custom element registry</span> is null:</p>
+
+    <ol>
+     <li><p>Set <var>inclusiveDescendant</var>'s <span
+     data-x="element-custom-element-registry">custom element registry</span> to
+     <span>this</span>.</p></li>
+
+     <li><p>If <span>this</span>'s <span>is scoped</span> is true, then <span data-x="set
+     append">append</span> <var>inclusiveDescendant</var>'s <span>node document</span> to
+     <span>this</span>'s <span>scoped document set</span>.</p></li>
+    </ol>
+   </li>
   </ol>